Process for removing cobalt from electrolytes



Patented May 31, 1949 PROCESS FOR REMOVING COBALT FROM ELECTROLYTES Dinsmore Laurence Griffith and Mavis Jean Rankin, Flin Flon, Manitoba, Canada, assignors to Hudson Bay Mining and Smelting Co., Limited, Winnipeg, Manitoba, Canada, a corporation of Canada No Drawing. Application December 26, 1946, Serial No. 718,604

1 Claim.

This invention relates to an improved process for removing cobalt from the electrolyte used in the electrolytic refining of zinc.

It has previously been proposed to add small amounts of antimony to the electrolyte as well as the usual additions of zinc dust and other precipitating agents in order to more completely precipitate the cobalt impurities in the solution. Such a process is described in Canadian Patent 322,278 (Skogmo and Spohn). According to the known process, an amount of antimony is added which is approximately equal to the weight of the cobalt content of the solution, or equa1 to the weight of cobalt that it is desired to remove from the electrolyte, some zinc plants having found it desirable to operate their electrolysis with an electrolyte containing up to about 8 mgs./l. of cobalt.

The deleterious effect of dissolved antimony in the final electrolyte has been found, however, to be so great that larger concentrations than about .04 mgs./l. completel overbalance any benefits derived from the use of antimony to precipitate cobalt. For this reason, known processes have kept additions of antimony to a minimum at the expense of having at best an incomplete precipitation of cobalt.

It has been found that by adding a much greater quantity of antimony, the cobalt may be completely eliminated from the electrolyte solution without materially raising the final antimony content.

According to the present invention, quantities of antimony varying from about 4 to about 10 times the weight of the cobalt to be removed are added to the electrolyte to efiect a much more complete precipitation of cobalt than was heretofore possible, without raising the amount of residual antimony in the electrolyte beyond a tolerable value. Generally speaking, it is found desirable to have a higher ratio of antimony to cobalt, the greater is the amount of cobalt in the electrolyte to be removed.

In accordance with the usual practice the electrolyte should contain a certain amount of copper in order to obtain satisfactor results in the removal of cobalt. It has been found that in the practice of the present invention the amount of copper contained in the solution is preferably rather higher than the amount generally used.

2 A range of about 0.5 to 1.5 grams per litre is satisfactory.

The following data serve to illustrate the advantages of the process of this invention over those previously used, but are not to be interpreted as a limitation of the scope of the invention.

Example I In using a known process with additions of antimony up to the same weight as the cobalt in the solution, the following data were recorded:

Mgs./l. Assay of cobalt in solution 9.0 Addition of antimony 10.0

Cobalt removed 3.2 Antimony remaining in solution .016

Example II According to the present invention, by adding a weight of antimony about four times the weight of the cobalt in solution, the following data were recorded:

Mgs./l. Assay of cobalt in solution 9 Addition of antimony 40 Cobalt removed 9 Antimony remaining in solution .016

Example III According to the present invention, by adding a weight of antimony about ten times the weight of the cobalt in solution, the following data were recorded:

Mgs./l. Assay of cobalt in solution 33.8 Addition of antimony 360 Cobalt removed 33.8 Antimony remaining in solution .020

4 REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 1,322,104 Gepp et al. Nov. 18, 1919 FOREIGN PATENTS 10 Number Country Date 322,278 Canada May 10, 1930 

